High volume pagewidth printing

ABSTRACT

A print assembly ( 14 ) for pagewidth inkjet printing that includes an elongate carrier that is mountable on a support structure ( 12 ) of a printer ( 10 ) in an operative position with respect to a platen ( 106, 108 ) of the printer. A number of printhead chips ( 186 ) are positioned on the carrier. The print head chips together define a print head that is configured to eject at least one billion drops per second into a printing zone defined between the print head and the platen of the printer. Control circuitry is also positioned on the carrier and is configured to control operation of the print head chips.

FIELD OF THE INVENTION

This invention relates to high volume pagewidth printing. Moreparticularly, this invention relates to a method of pagewidth printingand to a printer.

BACKGROUND OF THE INVENTION

High volume, high resolution printing is an objective that has beensought by the manufacturers of wide format printers for some time. Wideformat printers have been available to the public for many years.Examples of popular wide format printers are the Hewlett Packard (HP)1000/5000, the BP 3000/3500, the Epson 7000/10 000 and many others.

These printers all have a traversing printhead that traverses a printmedium while depositing ink on the medium. Applicant believes that theseprinters suffer from inherent disadvantages, particularly when attemptsare made to utilize the design of such printers in order to achievefaster printing speeds at high resolutions.

Central to the problem of achieving high printing speeds is the abilityto achieve a printhead that is capable of generating the necessarynumber of ink dots at a suitable rate. Further, in order to achieveaccurate printing, it is desirable that a row or band of the image becreated in as little print cycles as possible, and preferably in asingle print cycle. It follows that it is undesirable for a traversingprinthead to be used in an attempt to achieve high print speeds and thata single printhead incorporating a suitable number of inkjet nozzles isrequired.

Thermal printheads also referred to as bubble jet printheads andpiezoelectric printheads have been available for some time. These sufferfrom excessive heat build up and energy consumption and have thereforebeen found by the applicant to not be suitable for use in a pagewidthconfiguration. A number of disadvantages associated with such printheadsare set out in U.S. application Ser. No. 09/526,504.

The applicant has developed a printhead chip that is capable ofproducing images having a resolution as high as 1600 dpi. These chipsare manufactured using integrated circuit fabrication techniques.Details of the chips are provided in the above referenced applicationsand patents. Applicant believes that these printhead chips are extremelysuitable for use in wide format printers. The reason for this is thatsuch chips operate at extremely high speeds due to the large number ofnozzle arrangements required in a single chip and due to the fact thatsuch chips can be driven at an extremely high cyclical rate.

The Applicant has been faced with a number of difficulties in order toachieve the effective use of such printhead chips in wide formatprinters. One particular difficulty identified by the Applicant is theeffective control of a number of such printhead chips to achieveaccurate printing.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodof pagewidth printing, the method comprising the steps of:

feeding a print medium through a printing zone; and

ejecting drops of ink at a rate of at least one billion drops per secondfrom a print assembly on to the print medium in the printing zone togenerate an image on the print medium.

According to a second aspect of the invention, there is provided a printassembly for pagewidth inkjet printing, the print assembly comprising

-   -   an elongate carrier that is mountable on a support structure of        a printer in an operative position with respect to a platen of        the printer;

a number of printhead chips that are positioned on the carrier, theprinthead chips together defining a printhead that is configured toeject at least one billion drops per second into a printing zone definedbetween the printhead and the platen of the printer; and

control circuitry that is also positioned on the carrier and that isconfigured to control operation of the printhead chips.

According to a third aspect of the invention, there is provided aninkjet printer that comprises

a support structure;

a platen positioned in the support structure;

a print assembly positioned operatively with respect to the platen, theprint assembly comprising

-   -   an elongate carrier;    -   a number of printhead chips positioned on the carrier, the        printhead chips together defining a printhead that is configured        to eject at least one billion drops per second into a printing        zone defined between the printhead and the platen; and    -   control circuitry that is also positioned on the carrier and        that is configured to control operation of the printhead chips;        and

a feed mechanism positioned on the support structure for feeding a printmedium though the printing zone.

The invention is now described, by way of example, with reference to theaccompanying drawings. The following description is not intended tolimit the broad scope of the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 shows a schematic, three-dimensional view of part of a printingmechanism of a print assembly, in accordance with the invention, of aprinter, also in accordance with the invention;

FIG. 2 shows a front view of the printing mechanism of FIG. 1;

FIG. 3 shows a rear view of the printing mechanism of FIG. 1;

FIG. 4 shows a three dimensional, external view of the printer;

FIG. 5 shows a schematic, three-dimensional view of operative parts ofthe printer;

FIG. 6 shows a schematic, exploded view of the printer;

FIG. 7 shows a schematic, side sectioned view of a portion of theprinter incorporating the print assembly;

FIG. 8 shows an exploded view of an operative portion of the printingmechanism;

FIG. 9 shows a cross sectional view of an operative portion of theprinting mechanism;

FIG. 10 shows a high-level block diagram of a print engine controller ofthe printer;

FIG. 11 shows an expanded block diagram of a page expansion unit of theprint engine controller;

FIG. 12 shows a block diagram of the print engine controllerincorporating the page expansion unit;

FIG. 13 shows a schematic, three-dimensional view of part of a printheadchip of the print assembly of the printer, showing one nozzlearrangement of the printhead chip; and

FIG. 14 shows a schematic, three-dimensional view of a printhead modulethat incorporates a printhead chip.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 4, reference numeral 10 generally indicates a printer, inaccordance with the invention.

The printer 10 has a support structure 12 that supports a print assembly14 above a substrate. The support structure 12 includes a pair of spacedfeet 16 and a leg 18 extending from each foot 16. The print assembly 14is mounted on the legs 18 to span the legs 18.

A media tray 20 is positioned between the legs 18. The media tray 20 isconfigured to store suitable print media, such as paper 22.

The paper 22 is fed from a media feed mechanism in the form of a mediaroll 166 through the print assembly 14 and on to a take up spool 24. Anelectronics enclosure 26 is also positioned between the legs 18 toenclose various electronic components that are described below.

The print assembly 14 includes a lid 28, with a handle 30, and a frontcover 32. The lid 28 and front cover 32 are positioned between a pair ofend moldings 34.

The print assembly 14 also includes a color TFT LCD 36 with touch screennavigation. A stop button 38 is also provided to enable a user to stopoperation of the print assembly 14.

The print assembly 14 and its various components are shown in furtherdetail in the remaining Figures.

In FIGS. 1 to 3, reference numeral 40 generally indicates a printingmechanism of the print assembly 14. As can be seen in the drawings, theprinting mechanism 40 is segmented. In particular, the printingmechanism 40 includes nine printed circuit boards (PCB's) 42 connectedto each other with corresponding connector blocks 44.

The printing mechanism 40 further includes a printhead 41 havingseventy-two printhead modules 46. Each PCB 42 is configured to controleight printhead modules 46. It follows that nine PCB's 42 are provided.The printhead modules 46 are described in further detail below.

Each PCB 42 includes a print engine controller (PEC) 48. The PEC's 48are also described in further detail below.

Each PCB 42 also includes memory chips in the form of 64 Mbit externalDRAM chips 50. The DRAM chips 50 cooperate with the PEC 48 in a mannerthat is described below.

Further, each PCB 42 includes a quality authentication (QA) chip 52.Details of a suitable QA chip are set out in the above referenced U.S.application Ser. No. 09/113,053 and are therefore not set out in thisdescription. The QA chip 52 serves to inhibit unauthorized refilling ofink in the manner described in Ser. No. 09/113,053, in addition to otherfunctions such as ensuring the quality of print media used with theprinter 10.

An endmost PCB 42 includes a serial connector 54 that permits serialdata cables 56 to be connected to the PCB's 42.

Each PCB 42 is connected to its associated printhead modules 46 with aflexible PCB 58.

The printing mechanism 40 includes a metal chassis 60 that extendsbetween a pair of side moldings 61 that are positioned in the endmoldings 34. The PCB's 42 are mounted on the chassis 60. The chassis 60has a generally U-shaped cross section. A channel 62 of an Invar alloyis positioned on the chassis 60.

A chassis molding 64 of a plastics material is positioned on an outsideof the chassis 60 and the channel 62. Each PCB 42 is mounted on thechassis molding 64.

The chassis molding 64 defines a pair of recesses 66 on an outer side ofthe chassis molding 64. The recesses 66 extend a length of the chassismolding 64. A busbar 68 is positioned in each recess 66. The busbars 68are configured to supply electrical power to the PCB's 42.

An ink reservoir assembly 70 is positioned in the Invar channel 62. Theink reservoir assembly 70 includes an ink distribution arrangement 72.Each printhead module 46 is positioned on a respective ink distributionarrangement 72. In particular, each printhead module 46 is removablymounted on its ink distribution arrangement 72 to facilitate removal andreplacement when necessary.

The ink reservoir assembly 70 includes a plurality of ink reservoirmoldings 76. Each ink reservoir molding 76 corresponds with anassociated printhead module 46. The ink reservoir moldings 76 arepositioned end-to-end along and within the Invar channel 62. Each inkreservoir molding 76 defines a plurality of elongate ink channels 74,each accommodating a differently colored ink. Thus, effective elongateink channels extend a length of the Invar channel 62.

An end cap molding 78 is positioned on an endmost ink reservoir molding76. The end cap molding 78 has a plurality of connectors 80 definedthereon and in alignment with respective ink channels 74 when the endcap molding 78 is positioned on said endmost ink reservoir molding 76.The connectors 80 are connectable to an ink hose connector 82. The inkhose connector 82 is, in turn, connected to each of a plurality of inkhoses 84. It follows that each hose 84 is in fluid communication with arespective ink channel 74. Each hose 84 supplies the ink reservoirassembly 70 with ink of a particular color. For example, the hoses 84can carry Cyan (C), Magenta (M), Yellow (Y) and Black (K) inks,respectively. In this case, four hoses 84 are provided. Also, eachreservoir molding 76 defines four ink channels 74. Alternatively, thehoses 84 can carry Cyan (C), Magenta (M), Yellow (Y), Red (R), Green (G)and Blue (B) inks, respectively. In this case, six hoses 84 areprovided. Also, each reservoir molding 76 then defines six ink channels74. Instead of six differently colored inks, the six hoses 84 can carryCMYK and Infrared (IR) inks and a fixative (F) for high speed printingso that the inks can dry rapidly.

Each hose 84 is connected to a respective ink container 86 (FIG. 5), sothat each hose 84 is connected between an ink container 86 and aparticular ink channel 74. The hoses 84 are connected to theirrespective containers 86 with T-piece connectors 94 shown in FIG. 1.

The print assembly 14 includes a plurality of capping devices 88 thatcorrespond with respective printhead modules 46. Each capping device 88is displaceable between an operative position in which it serves to capits respective printhead module 46, to inhibit drying of ink, and aninoperative position in which ink can be ejected from the printheadmodule 46. A camshaft 90 is positioned in the chassis 60. A translatingmember 92 interconnects the camshaft 90 and the capping devices 88, sothat rotational movement of the camshaft 90 results in reciprocalmovement of the capping devices 88 between their operative andinoperative positions.

The camshaft 90 is driven with a suitable motor, indicated generally at96 in FIG. 5.

Further detail of the print assembly 14 is shown in FIG. 7. As can beseen in this drawing, the front cover 32, the lid 28 and a rear cover 98together define a housing 100 for the print assembly 14.

A plurality of ink cartridges 102 is positioned beneath the lid 28. Eachink cartridge 102 stores one of the inks mentioned above. Each inkcartridge 102 is positioned between a pair of clips 104 so that it canbe replaced when necessary. Each ink cartridge 102 and a respective inkreservoir 86 are in fluid communication with each other, when the inkcartridge 102 is received between the clips 104.

A pair of platens, in the form of an upper platen 106 and a lower platen108 is positioned within the housing 100. A pair of spaced primaryrollers in the form of an upper primary roller 110 and a lower primaryroller 112 is provided to displace the paper 22 through the printassembly 14. The upper roller 110 is positioned at an upper end of theplatens 106, 108, while the lower roller 112 is positioned between theplatens 106, 108. The rollers 110, 112 are configured to drive a sheetof the paper 22 over, consecutively, an inner surface of the lowerplaten 108 and an outer surface of the upper platen 106. Thus, the paper22 passes over the upper roller 110, while the lower roller 112 ispositioned between upwardly and downwardly moving portions of the paper22.

A brush 114 is pivotally mounted at 116 to the housing 100. The brush114 has an arcuate transverse profile that corresponds with the upperprimary roller 110. The brush 114 is positioned in the housing 100 sothat the paper 22 can pass between the brush 114 and the housing 100.

A pinch roller 118 is positioned downstream of the brush 114 to bearagainst the upper primary roller 110. Thus, when the paper 22 isdisplaced from between the brush 114 and the upper primary roller 110,the pinch roller 118 retains the paper 22 against lateral movement.

The upper platen 106 defines an upper printing zone 120 and a lowercutting zone 122. A gap 124 is defined between the upper and lowerprinting zones 120, 122. A plurality of spiked wheels 126 is partiallyreceived through the gap 124 to engage the paper 22 and the lowerprimary roller 112. A crossbar 128 is operatively positioned withrespect to the spiked wheels 126 to retain the spiked wheels 126 inposition. The spiked wheels 126 and the pinch roller 118 are configuredso that a suitable tension is set up in the paper 22 when the paper 22passes over the printing zone 120 of the upper platen 106.

The chassis 60 and channel 62 are positioned above the printing zone 120of the upper platen 106. The chassis 60 and the channel 62 are connectedto a displacement mechanism 129 so that the chassis 60 and channel 62can be displaced from the printing zone 120 when necessary. Inparticular, the chassis 60 and channel 62 are displaceable between anoperative position in which the printhead modules 46 are a distance fromthe printing zone 120 that is suitable for printing and an inoperativeposition in which the paper 22 can be released from the printing zone120.

The chassis 60 and channel 62 are connected to the pinch roller 118 withsuitable metalwork 130. Further, the chassis 60 and channel 62 areconnected to the crossbar 128. It follows that, when the displacementmechanism 129 is operated, the pinch roller 118 and the spiked wheels126 are displaced from the upper platen 106 together with the chassis 60and the channel 62.

The displacement mechanism 129 includes a camshaft 132 and a pusher 134.The pusher 134 is connected to the chassis 60 and the channel 62 sothat, upon rotation of the camshaft 132, the chassis 60 and channel 62are displaced towards and away from the printing zone of the upperplaten 106.

Upper idler rollers 136 are rotatably mounted above the upper platen 106so that the paper 22 is received between the upper platen 106 and theupper idler rollers 136.

A lower, sprung idler roller 138 is mounted on the lower platen 108 tobe partially received through a gap 140 defined in the lower platen 108.The sprung idler roller 138 is configured and positioned to bear againstthe lower primary roller 112. Thus, an upwardly moving portion of thepaper 22 is gripped, and passes between, the lower primary roller 112and the sprung idler roller 138.

The print assembly 14 includes a cutting mechanism 142 that is mountedin the housing 100 above the cutting zone 122 of the upper platen 106.The cutting mechanism includes a cutter 146 that traverses the paper 22to cut the paper 22. The cutting mechanism 142 includes an opticalsensor 144 so that the cutter 146 can be stopped when it reaches an endof a cutting stroke. The cutting zone 122 defines a cutting formation148 that cooperates with the cutter 146 to facilitate cutting of thepaper 22.

As can be seen in FIG. 6, the print assembly 14 includes an air impeller150 and a motor 152 to drive the air impeller 150. The air impeller 150serves to generate an air current within the housing 100 for coolingpurposes. An air filter 153 is also positioned in the housing 100 tofilter the air passing through the housing 100. The air impeller 150also serves to generate the air current to a sufficient extent tominimize the build up of dust on the printhead modules 46.

As can further be seen in FIG. 6, the primary rollers 110, 112 areconnected to a gearbox 154 that is mounted on a bracket 156. The gearbox154 and bracket 156 are positioned on one of the legs 18 and coveredwith one of the end moldings 34. Thus, the primary rollers 110, 112serve to drive the paper 22 through the print assembly 14.

A printhead bracket 157 is positioned in the housing 100 and extendsbetween the legs 18. The printhead bracket 157 provides a supportstructure for the chassis 60 and channel 62. The printhead bracket 157also provides a support structure for the upper idler rollers 136.

The housing 100 is shaped to define an opening 158 for passage of thepaper 22 into and out of the print assembly 14. Feed rollers 162 arerotatably mounted on a tie bar 160 that extends between the legs 18. Thefeed rollers 162 are positioned so that the paper 22 passes over thefeed rollers 162 when the paper is fed into the print assembly 14. Thetie bar 160 also serves a structural purpose in that it providesstructural rigidity to the printer 10.

Discharge rollers 164 are rotatably mounted on the upper platen 106. Thedischarge rollers 164 are positioned so that the paper 22 passes overthe discharge rollers 164 when the paper 22 is fed from the printassembly 14.

Both the media roll 166 and the take up spool 24 are driven with a mediaroll drive motor 168 and a take up spool drive motor 170, respectively(FIG. 5).

The printer 10 includes a power supply unit 172 that is positioned inthe electronics enclosure 26. The power supply unit 172 is configured tobe powered by either a 110V or 220V power supply. Further, the powersupply unit 172 is configured so that up to 90 Amps can be drawn fromthe power supply unit 172. The power supply unit 172 is connected withpower cables 173 to various components of the printer 10, such as thevarious drive motors to supply the components with required operationalenergy.

The printer 10 includes an ATX motherboard 174 that is also positionedin the electronics enclosure 26. A printhead interface card 176 ismounted on the motherboard 174. The printhead interface card 176 isconnected to the nine PCB's 42 with suitable data cables 178. Thus,conventional print data supplied to the interface card 176 from themotherboard 174 can be converted into a suitable form for reading by thevarious PCB's 42.

The printer 10 includes a hard drive unit 180. Conveniently, the harddrive unit 180 can have a capacity of 40 Gigabytes. This facilitates thestorage of entire images to be printed. The hard drive unit 180 isconnected to the motherboard 174 in a conventional fashion. The harddrive unit 180 is a conventional hard drive unit and is thereforecapable of storing images in any number of formats, such as thewell-known JPEG format. The manner in which the image data is read fromthe hard drive unit 180 is also conventional. As is set out below,printing of the images is digitally controlled as a result of theprinthead technology utilized in this invention. It follows thattransferal of image data from the hard drive unit 180 to the PCB's 42,via the printhead interface card 176 can take place without therequirement of significant data transformation, in particular, withoutthe requirement of digital to analogue signal conversion.

The interface card 176 is also connected to a motor and LCD controllerPCB 182 to control operation of the various drive motors and the TFTLCD. Details of such control are set out in the above referencedapplications and are therefore not provided in this description. Themotor and LCD controller PCB 182 is connected to a cut off switch 184that is, in turn, connected to the stop button 38 so that operation ofthe printer 10 can be halted.

As can be seen in FIG. 14, the printhead modules 46 each include aprinthead chip 186. The printhead chip 186 can be in the form of any ofthe printhead chips described in the above referencedapplications/patents. Each printhead module 46 includes a carrier 187 inwhich the printhead chip 186 is positioned. The carrier 187 defines asuitable connection zone for the flexible PCB 58 associated with theprinthead chip 186. FIG. 13 shows a schematic diagram of part of aprinthead chip 186 that is suitable for use in the printer 10. Eachprinthead module 46 includes what are known as on chip fiducials 258.The on chip fiducials 258 are essentially in the form of markers tofacilitate accurate alignment of the printhead modules 46 in the printassembly 14.

The printhead chip 186 is described in detail in the above referencedU.S. application Ser. No. 09/112,767 and will therefore not be describedin such detail in this specification. Briefly, however, the chip 186includes a wafer substrate 188. A CMOS drive circuitry layer 190 ispositioned on the wafer substrate 188 and is connected to the flexiblePCB 58.

A plurality of nozzle arrangements 210 is positioned on the CMOS drivecircuitry layer 190. For the purposes of convenience, one such nozzlearrangement 210 is shown in FIG. 13. The printhead chip 186 comprises amultiple replication of the nozzle arrangement 210 on the wafersubstrate 188. As set out in the above referenced applications andpatents, the printhead chip 186 is the product of an integrated circuitfabrication technique. Replication of components in order to achieve aproduct is a well-known feature of such a fabrication technique. Itfollows that the printhead chip 186 can readily be understood by aperson of ordinary skill in the field of chip fabrication.

Each nozzle arrangement 210 includes a thermal bend actuator 192 that ispositioned on the CMOS layer 190 to receive an actuating signal from theCMOS layer 190. In particular, the thermal bend actuator 192 includes asupport post 194 that is mounted on the CMOS layer 190 to extend fromthe CMOS layer 190. The thermal bend actuator 192 includes an actuatorarm 196 that is fixed to, and extends from, the support post 194. Theactuator arm 196 includes a heating layer 198 in the form of anelectrical heating circuit of a material having a coefficient of thermalexpansion that is such that the material is capable of performing usefulwork on a MEMS scale as a result of expansion upon heating. The heatinglayer 198 is positioned on a layer 200 of a material having acoefficient of thermal expansion that is less that that of the heatinglayer 198 defining the electrical heating circuit. The heating layer 198is positioned intermediate the layer 200 and the substrate 188 so thatthe actuator arm 196 is bent away from the substrate 188 when a currentis passed through the heating layer 198.

Nozzle chamber walls 202 are positioned on the CMOS layer 190. A roofwall 204 is positioned on the nozzle chamber walls 202. The nozzlechamber walls 202 and the roof wall 204 define a nozzle chamber 206. Theroof wall 204 defines an ink ejection port 208 from which ink isejected, in use.

A paddle member 212 is mounted on the actuator arm 196 to extend intothe nozzle chamber 206. The paddle member 212 is configured andpositioned in the nozzle chamber 206 so that, upon displacement of theactuator arm 196, as described above, ink is ejected from the nozzlechamber 206.

The actuator arm 196 is connected to the CMOS layer 190 through thesupport post 194 so that the heating layer 198 can receive an electricalsignal from the CMOS layer 190.

As can be seen in FIGS. 3 and 9, the printhead chips 186 are eachpositioned at an angle with respect to a straight line running thelength of the printing zone 120. This facilitates a measure of overlapat adjacent ends of the printhead chips 186 to ensure printingcontinuity.

It is clear from the above referenced United States applications andpatents that a pagewidth printhead including printhead chips asdescribed above can incorporate up to 84 000 nozzle arrangements. Itfollows that, by using the printhead chips 186, it is possible for theprint assembly 14 to have over as many as 200 000 nozzle arrangements.It follows that over 200 000 dots can be printed on the paper 22 in theprinting zone 120. In one particular example, the seventy-two printheadchips 186 provide a print width of 57.6 inches with 552 960 nozzlearrangements 210.

The nozzle arrangements 210 of each chip 186 are positioned side-by-sidein two rows in a staggered fashion. It follows that true 1600 dpiprinting can be achieved with the printhead chips 186.

Each printhead chip 186 therefore includes 7680 nozzle arrangements 210.Each nozzle arrangement 210 is independently controlled by the PCB 42 toeject a 1-picoliter drop on demand. The integrated circuit fabricationtechnology used is based on Very Large Scale Integration (VLSI)technology that is fully described in the above referenced applicationsand patents. As a result of the manufacturing techniques used, eachnozzle arrangement 210 can be as little as 32 microns wide. This allowseach printhead chip 186 to have a surface area as little as 21 mm².

The characteristics of each nozzle arrangement 210 are such that it iscapable of being driven at a cyclical rate of up to 80 kHz by itsassociated PEC 48. This permits printing of up to 21.6 billion drops persecond that provides thirty-five thousand square feet per hour at 1600dpi.

Each printhead chip 186 is connected to its associated PCB 42 with theflexible PCB 58. It follows that each flexible PCB 58 is connected tothe CMOS layer 190 of its associated printhead chip 186.

Each PEC 48 is a page rendering engine application specific integratedcircuit (ASIC) that receives input data relating to compressed pageimages from the printhead interface 176. The PEC 48 producesdecompressed page images at up to six channels of bi-level dot data asoutput. It will be appreciated that each PEC 48 communicates with eightprinthead chips 186 in this example. Each PEC 48 is capable, however, ofcommunication with up to sixteen such printhead chips 186. Inparticular, each. PEC 48 can address up to sixteen printhead chips in upto six color channels at 15 000 lines/sec. It follows that each PEC 48allows for a 12.8-inch printhead width for full bleed printing of A3, A4and letter pages.

Each PEC 48 is color space agnostic. This means that the PEC 48 canaccept print data in any color. While each PEC 48 can accept contonedata as CMYX or RGBX where X is an optional fourth channel, it can alsoaccept contone data in any print color space. Additionally, each PEC 48is configured to define a mechanism for arbitrary mapping of inputchannels to output channels. The PEC 48 is also configured for combiningdots for ink optimization and the generation of channels based on anynumber of other channels. In this example, data input is typically basedon CMYK for contone printing, K for a bi-level input, fixative, andoptional further ink channels. The PEC 48 is also configured to generatea fixative channel for fast printing applications.

Each PEC 48 is configured to be resolution agnostic. This means thateach PEC 48 simply provides a mapping between input resolutions andoutput resolutions by means of various scale factors. In this example,the expected output resolution is 1600 dpi. However, the PEC 48 does notstore any data to this effect.

Each PEC 48 is also configured to be page-length agnostic. Each PEC 48operates a printing band at a time and a page can have any number ofbands. It follows that a “page” can have any reasonable length.

Each PEC 48 defines an interface so that it can be synchronized withother PEC's 48, as is the requirement with this invention. This allows asimple two-PEC solution for simultaneous A3/A4/Letter duplex printing.This also allows each PEC 48 to be responsible for the printing of onlya portion of a page. It will be appreciated that combiningsynchronization functionality with partial page rendering allowsmultiple PEC's to be readily combined for alternative printingrequirements including simultaneous duplex printing, wide formatprinting, commercial printing, specialist high contone resolutionprinting, and printing applications where more than six ink channels arerequired.

The following table sets out the features of each PEC 48 and itsassociated benefits.

TABLE 1 Features and Benefits of PEC Feature Benefits Optimized printarchitecture 30 ppm full page photographic quality in hardware colorprinting from a desktop PC 0.18 micron CMOS High speed (>3 milliontransistors) Low cost High functionality 1.8 billion dots per secondExtremely fast page generation 15,000 lines per second 1.1 A4/Letterpages per PEC chip at 1600 dpi per second 1 chip drives up to Low costpage-width printers 122,880 nozzles 1 chip drives up to 6 99% ofprinters can use 1 color planes chip per page Sophisticated internalmemory Only requires 1 external memory, buffering and caching leading tolow cost systems JPEG expansion low bandwidth from PC low memoryrequirements in printer Lossless bitplane expansion high resolution textand line art with low bandwidth from PC (e.g. over USB) Netpage tagexpansion Generates interactive paper Stochastic dispersed dot Opticallysmooth image quality dither to moire effects Hardware compositor for 6Pages composited in real-time image planes Dead nozzle compensationExtends printhead life and yield Reduces printhead cost Color spaceagnostic Compatible with all inksets and image sources including RGB,CMYK, spot, CIE L*a*b*, hexachrome, YCrCbK, sRGB and other Color spaceconversion Higher quality/lower bandwidth Computer interface agnosticWorks with USB1, USB2, IEEE1394 (Firewire), ethernet, IEEE1284(Centronics) Variable page length Print any page length (up to 64 km)Cascadable in resolution Printers of any resolution Cascadable in colordepth Special color sets e.g. hexachrome can be used Cascadable in imagesize Printers of any width Cascadable in pages Printers can print bothsides simultaneously Cascadable in speed Very high speed printers can bebuilt Fixative channel data Extremely fast ink drying generation withoutwasteage Built-in security Revenue models are protected Undercolorremoval on Reduced ink useage dot-by-dot basis Does not require fontsfor No font substitution or high speed operation missing fonts Flexibleprinthead Many configurations of printheads configuration are supportedby one chip type Drives Memjet ™ printheads No print driver chipsrequired, directly results in lower cost Determines dot accurate Removesneed for physical ink ink usaege monitoring system in ink cartridges

In FIG. 10, there is shown a block diagram of the PEC 48. The PEC 48includes a high-speed interface 214 through which an external microcontroller 216 can write to the 64 Mbit DRAM chip 50. The PEC 48 alsoincludes a low speed serial interface 220 through which the microcontroller 216 can access registers of the PEC 48 and the DRAM chip 50.

The PEC 48 also includes a page expansion unit (PEU) 222 that receivesdata relating to compressed pages and renders it into data relating tobi-level dots. A line loader/formatter unit 224 is also provided thatformats dots for a given print line destined for a printhead interface226 that communicates directly with the printhead chips 186 of eachprinthead module 46.

As can be seen, the PEC 48 performs three basic tasks. These are:

-   -   a) Accepting register and DRAM access commands via the low speed        interface 220 (or from the external DRAM chip 50).    -   b) Accepting DRAM write accesses (typically compressed page        bands and register command blocks) via the high speed interface        214.    -   c) Rendering page bands from the external DRAM chip 50 to the        printhead chips 186.

These tasks are independent. However, they do share the external DRAMchip 50. It follows that arbitration is required. The PEC 48 isconfigured so that DRAM accesses required for rendering page bandsalways have the highest priority.

The PEC 48 includes a PEC controller 228 that provides external clientswith the means to read and write PEC registers, and read and write DRAMin single 32 bit data chunks.

The DRAM chip 50 is connected to an SDRAM controller 234. In turn, theSDRAM controller 234 is connected to a DRAM interface unit 236.

The PEC 48 includes a data bus 230 and a low speed serial bus 232. Boththe SDRAM controller 234 and the DRAM interface unit 236 are connectedto the low speed serial bus 232. The PEC controller 228 is connected tothe data bus 230. The PEC controller 228 is also connected to the lowspeed serial bus 232 via the low speed interface 220. The high-speedinterface 214, the PEU 222 and the line loader/formatter unit are alsoconnected to the data bus 230.

In use, since the PEC 48 prints page bands from DRAM, a given band B isloaded into DRAM via the high-speed interface 214 before printing canbegin. Then, while the PEC 48 is rendering band B via the PEU, band B+1can be loaded to DRAM. While band B+1 is being expanded and printed,band B+2 can be loaded, and so on.

In the following table, the various components of the PEC 48 mentionedabove are described briefly.

TABLE 2 Units within PEC (high level) unit reference acronym unit namenumeral description DIU DRAM 236 Provides the interface for DRAMinterface read and write access for the unit various PEC units. The DIUprovides arbitration between competing units and passes on DRAM requeststo the SCU. HSI High 214 Provides external clients (such speed as themicrocontroller) interface with the means to write to DRAM. LLFU Lineloader 224 Reads the expanded page image formatter from line store,formatting the unit data appropriately for the Memjet printhead. LSI Lowspeed 220 Provides external clients with interface the means to sendcommands to the PCU and receive register reads. PCU PEC 228 Providesexternal clients with controller the means to read and write PECregisters, and read and write DRAM in single 32-bit chunks. PEU Page 222Reads compressed page data and expansion writes out the decompressedform unit of the same to DRAM. PHI Printhead 226 Is responsible forsending dot interface data to the Memjet printhead segments and forproviding line synchronization between multiple PECs. SCU SDRAM 234Provides the DIU with access controller to the external DRAM. unit

An expanded block diagram of the PEU 222 is shown in FIG. 11. In thefollowing table, the various components of the PEU 222 are describedbriefly.

TABLE 3 Units within Page Expansion Unit (high level) unit referenceacronym unit name numeral description CDU Contone 238 Expands JPEGcompressed decoder contone layer and writes unit decompressed contone toDRAM CLBI Contone line 240 Provides line buffering buffer between CRUand HCU interface CRU Contone 242 Reads expanded contone image readerunit from DRAM DNC Dead nozzle 244 Compensates for dead nozzlescompensator by error diffusing dead nozzle data into surrounding dots.DWU Dotline 246 Writes out the 6 channels of writer dot data for a givenprint- unit line to the line store DRAM HCU Halftoner 248 Ditherscontone layer and compositor composites the bi-level spot unit 0 andposition tag dots. LBD Lossless 250 Expands compressed bilevel bi-levellayer. decoder SLBI Spot line 252 Provides line buffering buffer betweenLBD and HCU interface TE Tag encoder 254 Encodes tag data into line oftag dots. TLBI Tag line 256 Provides line buffering buffer between TEand HCU interface

A first stage in page expansion occurs along a pipeline defined by theCDU 238/CRU 242, the LBD 250 and the TE 254. The CDU 238 expands aJPEG-compressed contone (typically CMYK) layer. The LBD 250 expands acompressed bi-level layer (typically K), and the TE 254 encodes datatags for rendering (typically in infra-red ink) at a later stage. TheCLBI 240, the SLBI 252 and the TIBI 256 receive output data from thisstage.

The HCU 248 carries out a second stage. The HCU 248 dithers a contonelayer and composites position tags and a bi-level spot0 layer over aresulting bi-level dithered layer. A data stream generated by the HCU248 is adjusted to create smooth transitions across overlapping segmentsor printhead chips 186. The HCU 248 is configured so that a number ofoptions exist for the way in which compositing occurs. This stage canproduce up to six channels of bi-level data. It should be noted that notall six channels might be present on the printhead chips 186. Forexample, the printhead chips 186 may be CMY only, with K pushed into theCMY channels and IR ignored. Alternatively, the position tags mentionedabove may be printed in K if IR ink is not available or for testingpurposes.

The DNC 244 carries out a third stage. In this stage, the DNC 244compensates for dead nozzles in the printhead chips 186 by errordiffusing dead nozzle data into surrounding dots.

Bi-level, six channel dot-data (typically CMYK-IRF) generated in theabove stages is buffered and written out to a set of line buffers storedin the off-chip DRAM via the DWU 246.

In a final stage, the dot-data is loaded back from the DRAM, formattedfor the printhead, and passed to the printhead interface 226 via a dotFIFO (not shown). The dot FIFO accepts data from the lineloader/formatter unit 224 at pclk rate, while the printhead interface226 removes data from the FIFO and sends it to the printhead chips 186at a rate of either pclk/4, pclk/2 or pclk.

FIG. 12 simply shows the PEC 48 incorporating the exploded PEU 222.

The printing benefits associated with the printhead chips 186 are setout in detail in the above referenced applications and patents. However,some benefits are particularly important when applied to wide printingformats.

A particular benefit is the high number of nozzle arrangements 210 perprinthead chip 186. This facilitates extremely rapid printing in that asingle print cycle can achieve an image band. It follow that it is notnecessary for further print cycles to be used to fill in “missing” dotsas is the case with a scanning printhead.

The PEC's 48 provide the necessary synchronized control of the printheadchips 186 as described above. Furthermore, as is clear from a number ofthe above referenced applications and patents, for example Ser. No.09/113,053, the printhead chips 186 allow for the conversion fromanalogue printing processes to fully digital processes. This allows fora substantial amount of flexibility and speed. Digital control of theprinthead chips 186 is by means of the PEC's 48. The fact that the PEC's48 digitally control the printhead chips 186 allows for the highprinting speed of up to 21.6 billion drops per second. In particular,the need for separate printhead chip drivers is removed, which is key tothe high printing speed of the chips 186.

The incorporation of the CMOS layer 190 serves to integrate CMOStechnology with MEMS technology on each printhead chip 186. It followsthat at least one off-chip connection for each nozzle arrangement 210 isnot required. It will be appreciated that such a requirement would makea printhead unreliable and cost-prohibitive to manufacture.

A further important advantage associated with the printer 10 is that awidth of the printing zone 120 is extremely small when compared to thelength. In a particular example, the printing zone 120 can be as littleas 0.5 mm thick. It will be appreciated that it is necessary to achieveextremely stable paper movement through the printing zone 120 in orderto ensure that accurate printing takes place in the printing zone. Thenarrow width of the printing zone 120 facilitates minimal control overthe paper 22 as it passes through the printing zone.

In the event that a substantially wider printing zone were provided, itwould be necessary to provide further control over movement of the paper22 through such a printing zone. This would require such devices asvacuum platens to retain the paper 22 against any form of pivotal orlateral movement as the paper 22 moves through the printing zone. Thiscould greatly increase the cost of the wide format printer.

This highlights some reasons why thermal or bubble jet and piezoelectricprintheads would not be practical choices when attempting to achieve theprinting characteristics of the printer 10. As set out in the abovereferenced applications and patents, such printheads are not suitablefor providing the high density of nozzle arrangements achieved with theprintheads of the above referenced matters. It follows that, inattempting to apply thermal and piezoelectric printheads to a wideformat printer, it would be necessary to have a relatively wide printingzone so that overlapping of printheads could occur to the necessaryextent. This would immediately raise the problem mentioned above. Stillfurther, especially with the thermal printheads, a suitable coolingsystem would be required to keep the temperature in the printing zone ata reasonable level. This would also increase the cost to an unacceptablyhigh level.

In order to achieve an appreciation of the speed of the printer 10 at aresolution of 1600 dpi, the following comparative table is set outbelow. It should be noted that the purpose of the following table issimply to illustrate the speed of printing and is not intended todenigrate the various printers used as comparators.

WIDE FORMAT PRINTERS - 100 TIMES FASTER Memjet OEM Printhead Print Width(inches) 38.4 44.8 51.2 57.6 64.0 70.4 76.8 Number of Printhead Chips 4856 64 72 80 88 96 Number of Nozzles 368,640 430,080 491,520 552,960614,400 675,840 737,280 Max. print speed (sq ft/hr at 1600 × 1600 dpi)17,578 20,508 23,438 26,367 29,297 32,227 35,156 Make Model ResolutionSpeed Memjet Speed Advantage (# of times faster) Com- HP 1000/5000 600 ×600 120 146 171 195 220 244 269 293 parison HP 3000/3500 600 × 300 72244 285 326 366 407 448 488 Epson 7000/10000 720 × 720 90 195 228 260293 326 358 391 Encad Novajet 800 600 × 600 96 183 214 244 275 305 336366 Gretag Arizona Draft mode 444 40 46 53 59 66 73 79 Gretag Arizona309 × 618 220 80 93 107 120 133 146 160 Colorspan Mach X11 600 × 600 115153 178 204 229 255 280 306 Canon BJW 9000 600 × 1200 72 244 285 326 366407 448 488 Mutoh Albatross 792 × 792 65 270 316 361 406 451 496 541Roland HiFi Jet 720 × 720 96 183 214 244 275 305 336 366 Nur Fresco 360× 360 300 59 68 78 88 98 107 117

As is known by those of skill in the fabrication of integrated circuits,while a set up cost for the manufacture of an integrated circuit devicecan be high, the cost of commercial manufacture of such devices isrelatively low. It follows that Applicant envisages that the cost ofmanufacture of a wide format printer in accordance with this inventionwill be comparable to the cost of manufacture of the wide formatprinters listed in the above table.

1. A print assembly for pagewidth inkjet printing, the print assemblycomprising an elongate carrier that is mountable on a support structureof a printer in an operative position with respect to a platen of theprinter; a number of printhead chips positioned on the carrier, theprinthead chips each having a plurality of ink ejection nozzlearrangements on a wafer substrate, each nozzle arrangement having anactuator for ejecting ink from an associated nozzle when a resistiveelement of said actuator is heated by an electrical current supplied bydrive circuitry on the wafer substrate; and a plurality of controllers,each controller mounted on a respective printed circuit board that ispositioned on the carrier, each controller being connected to aplurality of the printhead chips via individual flexible printed circuitboards of each printhead chip and to the other controllers, and eachcontroller being configured to control operation of at least 10,000nozzle arrangements of the connected printhead chips.
 2. A printassembly as claimed in claim 1, in which the printhead chips togetherincorporate at least one hundred thousand nozzle arrangements.
 3. Aprint assembly as claimed in claim 1, in which the printhead chipstogether incorporate at least two hundred thousand nozzle arrangements.4. A print assembly as claimed in claim 3, which includes between fortyand one hundred printhead chips positioned on the carrier.
 5. A printassembly as claimed in claim 1, in which each printhead chip is theproduct of an integrated circuit fabrication process.
 6. A printassembly as claimed in claim 5, in which and the drive circuitry iscomprised in a CMOS drive circuitry layer positioned on the wafersubstrate with the nozzle arrangements positioned on the wafer substrateand the CMOS drive circuitry layer.
 7. A print assembly as claimed inclaim 6, in which each nozzle arrangement is electrically connected tothe CMOS drive circuitry layer.
 8. A print assembly as claimed in claim7, which includes a plurality of printhead modules, each printheadmodule incorporating a printhead chip, the printhead modules beingmounted on the carrier.